tailieunhanh - Sonar Technology Advances
The basic idea behind any sonar system is as follows: an acoustic signal (or ping) is emitted by the sonar into an area to be observed; the sonar then listens for echoes of the ping that have been produced when bouncing back from the objects that might be present in the area. Typically, sonar images are produced by plotting the intensity measured back by the sonar versus time, and since the speed of sound underwater is known (or can be measured), the time axis effectively corresponds to range from the sonar. In this way, just as light illuminates a scene.
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